Over the past 40 years, chronic stress has been increasingly implicated in a wide and growing variety of humanity's most lethal and life-altering diseases. These include such severe conditions as diabetes, Alzheimer's disease, heart attacks, depression, osteoporosis, and immunosuppression, as well as nonlethal but still unfortunate problems like common colds, back pain, and even erectile dysfunction. In fact, scientific literature shows that stress affects life expectancy in developed countries more than genetics and behavioral factors such as smoking.
Given the enormous impact of stress on human life and health worldwide, there is great potential in measuring and treating stress on a population-wide scale. Although stress is often described as a subjective emotional state, medically it has important biochemical and physiological effects. These effects that can be quantified, such as increased levels of a group of certain hormones including the glucocorticoids and catecholamines. However, physiological concentrations of these hormones, even when elevated, are often extremely low in tears, saliva and serum (38.9±15.5, 46.3±16.0, and 489.7±177.4 nM respectively), making precise measurement a continuing technical challenge.